New record of Pampahippus secundus (Mammalia, Notoungulata) from the Upper Lumbrera Formation, Eocene of northwestern Argentina

GARCÍA-LÓPEZ, DANIEL A.; DERACO, VIRGINIA; ROUGIER, GUILLERMO W.; DEL PAPA, CECILIA; BABOT, JUDITH; BERTELLI, SARA; HERRERA, CLAUDIA M.; GIANNINI, NORBERTO P.

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Año: 2019 vol. 39

0272-4634

The Paleogene record of notoungulates in Northwestern Argentina is relatively abundant and most taxa are endemic. Additionally, until now different fossil-bearing units have no species in common, preventing biostratigraphic correlations, general comparisons for some fossil-bearing units, and the discovery of biogeographic patterns. Here we present a new specimen of Toxodontia coming from levels of the Upper Lumbrera Formation in the locality of El Simbolar, Salta Province. This new specimen is a fragmentary left dentary preserving a partial p4 and m1-2 and is here referred to the species Pampahippus secundus based on the presence of a bunoid and isolated entoconid on the lower premolars, a diagnostic feature for the genus. Additionally, the mandibular and dental size matches the measurements of the mentioned species. This new material provided information about the lower molars (particularly the m1 and m2), previously unknown for this taxon. The anterior molars are remarkably conservative in morphology and very similar to Pampahippus arenalesi regarding the arrangement of the cristida obliqua, hypolophid, and the development of the accessory cuspule in the trigonid. Nevertheless, the molars also show anatomical singularities, as the lesser development of cingulids and the particular arrangement of the paracristid. Besides the anatomical information, this record expands the biochron of the species from Lower Lumbrera to Upper Lumbrera Formation, being thus the first mammal common to both units. This also underlines that the entire significance of the record of native ungulates in Northwestern Argentina remains to be evaluated in light of new discoveries.